1. Field of the Invention
The present invention relates to a patient monitoring system comprising at least one body sensor for detecting a physiological parameter, as well as, connected downstream from the body sensor, at least one of a body signal processing unit and a therapy device designed for acting on a patient, and a mobile radio end unit designed for transmitting data from at least one of the body signal processing unit and the therapy device to a central monitoring station, said mobile radio end unit being operable in a cellular mobile radiotelephone network having a multiplicity of preferably ground-based base stations, wherein a base station coordinate memory unit is provided and a rough locator unit for a rough determination of a patient""s current location based on rough positioning information obtained from a current base station connection of the mobile radio end unit in tie mobile radiotelephony network.
2. Background Art
In cases of serious health impairments and/or after major surgery such as, for instance, after a heart transplant for an early detection of a possible rejection, it is advisable to provide for a long-term uninterrupted monitoring of the patient""s condition. In view of the affected person""s quality of life, but also for reasons of capacity and cost this should take place outside of a clinic.
For wearers of electromedical implants, such as cardiac packers, constant monitoring of the condition of the patient or device is necessary in some cases as well, and, as a rule, it is desirable to at least have the option to immediately signal a life-threatening condition of the patient or device along with a simultaneous determination of the patient""s whereabouts.
A number of known systems for ambulatory patient monitoring exist for various applications.
In U.S. Pat. No. 5,626,630 A1, a medical telemetry system using an implantable quasi-passive transponder is described, which, in addition to the transponder, incorporates a relay device to be worn externally by the patient, and a remote monitoring station.
In DE 197 58 939 A1, a patient monitoring system is described whereby a patient device is automatically activated in response to a certain location of the patient for data transmission to a central monitoring station, in particular over a telephone network.
WO 97/00708 A1 describes an advanced, highly complex system for world-wide patient locating and data transmission from device implants to suitable analysis points. In order to determine the patient""s geographic location based on the satellite positioning system GPS, the system incorporates a special receiver, which the patient carries with him.
The location of the patient is determined in the same complex manner with the cardiac stimulation system with expanded communication and monitoring options according to U.S. 5,720,770 A1, which in other respects also provides for the use of the fixed telephone network or of a cellular network for the transmission of relevant data.
In the applicant""s German patent application 198 44 296.3, a patient monitoring and locating system is revealed that is operated with the assistance of a mobile radiotelephone end unit, on the basis of a cellular network, such as, e.g., the GSM network. The process entails a rough location determination with the aid of a base station coordinate memory unit and a rough locator unit connected to the former. The locating method used there is based on utilizing the location-relevant information that is constantly available internally in a cellular mobile radiotelephone network to determine the patient""s location, forgoing separate means for geographic positioning.
This idea is based, on one hand, on the fact that the geographic coordinates of all utilized base stations are available at the mobile radiotelephone network operator""s and that each registered end unit is, of course, located within the range of transmission and reception of at least one base station, however, normally within the range of multiple base stations at the same time. At the switching level of the mobile radiotelephone system, information is also available as to which base station it is, so that an approximate determination of the patient""s location is possible based on the base station location data set alone.
Furthermore, in a modem mobile radiotelephone system, measurements of among others, the signal delay time take place at least to the base station that is currently active for the given end unit, so that the automatic handover can take place between different base stations, which means that a further piece of location-relevant information is present in the system, in the form of the signal delay time information. If the respective shortest signal delay times to multiple adjacent base stations are measured at the same time, their location data and corresponding signal delay time values may be used to obtain a very precise, two-dimensional determination of the location of the respective end unit and thus of the patient. Depending on the specific structure of the network, the signal delay time data may be queried at the end units or at the base stations, and optionally also at the switching level.
Lastly, the fact that the base stations, as a rule, operate with directional antennas principally offers a possibility to fine-tune the determination of the patient""s location by determining and analyzing with which base station antenna the connection to the patient""s end unit is maintained.
The above locating measures have the shortcomingxe2x80x94also in the case of signal delay time measurementsxe2x80x94that the location resolution is within a magnitude of only ten to several hundred meters in dependence upon the cell size of the mobile radiotelephone network. This location resolution regarding the location of persons in an emergency situation is too rough to quickly locate the person in question in densely populated areas, such as inner city areas with multi-story multi-family homes or business offices and large crowds in which it is difficult to find a person, such as during big events. However, this analogously also holds true for very large mobile radiotelephone cells, for instance in the mountains or in the countryside.
To solve this problem, the invention now proposes, in addition to the rough location determination known from the prior art, to supplement the monitoring system with a three-dimensional fine locator unit incorporating, in the mobile radiotelephone end unit, a direction-finding transmitter that transmits a direction-finding signal, and a separate direction-finding device for the fine locating of the direction-finding signal, and thus of the mobile radiotelephone end unit, after the rough position determination.
Based on this configuration of the monitoring system, the mobile radiotelephone end unit of the monitored patient can be roughly located in the known manner when an emergency call is received, and an emergency response team can be dispatched to that location. This team is equipped with the direction-finding device and can, after arriving at the given location, switch the direction-finding transmitter of the mobile radiotelephone end unit of the monitored patient to a continuous send mode. Alternately, the direction-finding transmitter of the fine locator unit may also be turned on remotely by the operator of the mobile radiotelephone network himself. In other respects it is also advantageous in both cases if the direction-finding transmitter is formed by the transmitting portion of the mobile radiotelephone end unit itself.
The direction-finding device, too, is preferably formed by a modified standard mobile radiotelephone unit so that the fine locating may be implemented, for example, on the basis of the conventional GSM technology. This merely requires corresponding software adaptations in the operating programs of the mobile radiotelephone end units. The only relevant hardware addition that is then required, is to provide the mobile radiotelephone end unit with a direction-sensitive antenna which, in a standard mobile radiotelephone end unit, is a very simple process.
The fine locating on the basis of the direction-sensitive receive antenna may then lastly be perfected with a fine-resolution field strength indicator for the received direction-finding signal. Since the hardware technology of conventional GSM standard mobile telephones includes a field strength measuring device, this means that, again, only a software adaptation is required to implement a high-resolution numeric indicator in the display window of the end unit.
Advantageous improvement of the invention will, in other respects, be illustrated in greater detail below, in combination with the description of the preferred embodiment of the invention based on the figures.